Hi @Frank_Heijtlager ,
perhaps this dirty workaround will help still the numbers are released by Microsoft:
Extend the phone number by a suffix at the end of the phone number for each user. Then go to your SBC and create a number manipulation to add this suffix by inbound calls and to remove the suffix by outgoing calls.
When Microsoft fixed it, you can assign the correct phone numbers again and remove the number manipulation in your SBC.
With PowerShell it should be easy to assign a suffix to each user. I would use the same suffix, so it is easier to identify. And plese inform your users, that this is just a workaround. The temporary number will be visible for your end users in the calling app.